#include <bits/stdc++.h>
#include <cassert>

using namespace std;
using ll = long long;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define pb push_back
#define ff first
#define sc second

mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
template<typename T>
void shuf(vector<T>& a) {
    for (int i = 1; i < sz(a); i++) swap(a[i], a[rnd() % (i + 1)]);
}

const int mod = 1e9 + 7;
int sum(int x, int y) {
    return (x + y >= mod ? x + y - mod : x + y);
}
int mul(int x, int y) {
    return (x * 1ll * y) % mod;
}

void solve() {
    int n, k; cin >> n >> k;
    k--;
    vector<vector<int>> dp(n + 1, vector<int>(n + 1));
    dp[1][0] = 1;
    for (int np = 2; np <= n; np++) {
        for (int cnt = 0; cnt <= k; cnt++) {
            dp[np][cnt] = sum(mul(cnt + 1, dp[np - 1][cnt]), (cnt == 0 ? 0 : mul(np - cnt, dp[np - 1][cnt - 1])));
        }
    }
    cout << dp[n][k] << '\n';
}

signed main() {
    int tt = 1;
    #ifdef LOCAL
        freopen("in.txt", "r", stdin);
        freopen("out.txt", "w", stdout);
        cin >> tt;
    #else
        ios::sync_with_stdio(false);
        cin.tie(0); cout.tie(0);
    #endif

    while (tt--) {
        solve();
    }

    return 0;
}